They first appeared during the Devonian period around 415 to 360 million years ago, but the only known specimen of E. kawai has been dated to the Late Cretaceous at the height of the rabbitfish's reign.

Unlike the sharks and rays to which they are related, most rabbitfish have a single set of teeth that do not grow back and are used for grinding their food.

These teeth, along with the position of the mouth so that it is the underside of the head, allows the rabbitfish to graze on the sea bed much like a herbivore would do on land.

This opened up a range of new prey to the fish, which would have been able to scavenge food and rip flesh from decaying carcasses, unlike others in its group, which would only have been able to crush organic matter.

However, some have argued that the remains of E. kawai are actually those of another prehistoric cartilaginous fish, Ischyodus, which lived about the same time and has also been compared to the rabbitfish Chimaera monstrosa.